In recent years, there is a demand for a semiconductor device having a high-speed operation and a low power consumption. For example, in order to realize low resistance of a source/drain contact or a gate electrode of a metal-oxide-semiconductor (MOS), a silicide is formed by a salicide process. As the silicide, attention is given to a nickel silicide (NiSi) capable of consuming a small amount of silicon and having low resistance.
To form a NiSi film, there is widely used a method in which a nickel (Ni) film is formed on a silicon substrate or a polysilicon substrate by a physical vapor deposition (PVD) process, such as a sputtering or the like, and then subjected to an annealing under an inert gas atmosphere (see, e.g., Japanese Patent Application Publication No. H09-153616 (corresponding to U.S. Pat. No. 5,840,626)).
Further, the Ni film itself may be used for a capacitor electrode of DRAM.
However, such PVD process has poor step coverage. For this reason, along with miniaturization of semiconductor devices, there has been proposed a method for forming the Ni film by a chemical vapor deposition (CVD) process having a better step coverage (see, e.g., International Application Publication No. WO2007/116982).
When the Ni film is formed by the CVD process, a nickel amidinate is used as a film forming source material (precursor) and NH3 is used as a reduction gas. In this case, however, N (nitrogen) is included in process gases and thus introduced into the film. Accordingly, the nickel nitride (NiXN) is formed during the Ni film forming process, and the resulting Ni film includes impurities such as N (nitrogen), having high resistance.
To solve the foregoing problems, International Application Publication No. WO2011/040385 discloses a method of removing the N in the film by modifying the film under a hydrogen atmosphere after the Ni film including the N is formed by using a nickel amidinate and NH3.
However, the addition of such post process after forming the film causes an increase in a process time, which leads to a decrease of throughput. Further, in the method described in International Application Publication No. WO2011/040385, the film forming process and the modification process need to be repeatedly performed multiple times to raise the purity of the Ni film, so that the process time becomes longer.